Tag Archives: thiamine

Thiamine diphosphate synthesis and redox state indicator in rat brain during of B(1) hypovitaminosis

Yu. M. Parkhomenko, A. S. Pavlova, O. A. Mejenskaya,
S. P. Stepanenko, L. I. Chekhivska

Palladin Istitute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv;
e-mail: yupark@biochem.kiev.ua

The main aim of this study was to reveal the relationship between thiamine metabolism and the redox balance of cellular metabolism in chronic alimentary thiamine deficiency. On the experimental model of chronic alimentary thiamine deficiency (hypovitaminosis) the dynamics of changes in the indicators of thiamine diphosphate (ThDP) synthesis and the redox state in rat brain tissue were studied. In the whole brain homogenate of the rat, the levels of ThDP and thiamine pyrophosphokinase (TPK) activity as well as the levels of free SH-groups and reactive oxygen species (ROS) were measured. The results obtained showed, even with a very limited intake of thiamine into the body (model of alimentary hypovitaminosis), there was no increase in the level of ROS (one of the signs of oxidative stress) in the brain tissue, while the level of free SH-groups significantly decreased. Under these conditions, the content of the coenzyme form of thiamine, ThDP, in brain tissue changes insignificantly, which suggests that there are non-coenzymatic mechanisms of vitamin B1 involvement in maintaining cellular redox homeostasis. The analysis of changes in the ThDP content and the TPK activity in the cerebral cortex, cerebellum and hippocampus of the rats’ brain in the dynamics of  hypovitaminosis  development and TPK immunoreactivity at the end of the experiment  showed that the ThDP synthesis in cells of various brain regions under the indicated conditions does not depend  on the redox  state, but is regulated by the level of ThDP.

Oxidized derivatives of thiamine: formation, properties, biological role

Yu. M. Parkhomenko1, I. I. Stepuro2, G. V. Donchenko1, V. I. Stsiapura3

1Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv;
e-mail: yupark@biochem.kiev.ua;
2Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, Grodno;
e-mail: biophyz@biochem.unibel.by;
3Yanka Kupala University of Grodno, Belarus;
e-mail: vstepuro@grsu.by

The data available in literature about formation, properties, possible biological role and practical application of the oxidized derivatives of В1 vitamin (thiamine) is first generalized and analysed in the review. It is known that at the values of рН > 7.0 the molecule of thiamine is able to undergo two-phase reaction of opening of thiazole ring with formation of anion of thiol form of thiamine and unstable tricyclic form. In the presence of oxidants in an alkaline environment a thiol form of thiamine is oxidized to thiamine disulfide, tricyclic form – to thiochrome. Oxidative transformation of thiamine molecule is promoted by phenoxyl radicals, their level can be substantially increased in animal tissues at oxidizing stress of different origin when the level of reactive forms of oxygen sharply increases and content of hemoproteins oxoferryl forms is raised. The analysis of literature data gives grounds to assume that thiamine and its hydrophobic metabolite – thiochrome – under certain conditions can perform an important antioxidant function in protection of cell structures against damaging action of peroxinitrite, nitrogen dioxide, peroxide. The presence of oxidized metabolites of thiamine and its phosphates in the cells of animals, even in minor quantities, is an established fact and, consequently, there is a possibili­ty, that they can interact specifically with cellular structures or proteins to effect cellular processes in certain conditions.